Method and system for reselecting an access point

• US 20060258350A1
• Filed: 12/28/2005
• Published: 11/16/2006
• Est. Priority Date: 05/11/2005
• Status: Active Grant

• Current Assignee: Interdigital Technology Corporation (InterDigital, Inc.)
• Original Assignee: Interdigital Technology Corporation (InterDigital, Inc.)
• Inventors: Marinier, Paul, Rudolf, Marian, Roy, Vincent, Cuffaro, Angelo
• Granted Patent: US 8,190,155 B2
• Time in Patent Office: Days
• US Class Current: 455/435.100
• CPC Class Codes: H04W 36/0061 of neighbour cell information
• CPC Class Codes: H04W 36/08 Reselecting an access point
• CPC Class Codes: H04W 84/12 WLAN [Wireless Local Area Networks]

Abstract

A list of candidate basic service sets (BSSs) or access points (APs) is included in a medium access control (MAC) message which is received at a wireless transmit/receive unit (WTRU). The list includes an identity of each candidate BSS or AP and a preference indicator which indicates an extent that the candidate BSS or AP is preferred for selection and whether the candidate BSS or AP shall not be considered for selection. A BSS or AP is selected by the WTRU using the list.

Claims

1. A wireless local area network (WLAN) access point comprising:

a medium access controller (MAC) configured to produce a list of candidate basic service sets (BSSs) for performing a wireless transmit/receive unit (WTRU) BSS selection, the candidate BSSs list including an identity of each candidate BSS and a preference indicator which indicates an extent that the candidate BSS is preferred for selection and whether that candidate BSS shall not be considered for selection; and

a transceiver configured to transmit the candidate BSSs list.

2. The WLAN access point of claim 1 wherein the candidate BSSs list indicates a frequency channel of each candidate BSS.

3. The WLAN access point of claim 1 wherein the candidate BSSs list indicates for each candidate BSS a channel occupancy of that BSS.

4. The WLAN access point of claim 1 wherein the transceiver is configured to transmit an expiration time associated with the candidate BSSs list.

5. The WLAN access point of claim 1 wherein the candidate BSSs list is sent in a body of a MAC frame.

6. The WLAN access point of claim 1 wherein the transceiver is configured to receive a request for the candidate BSSs list and the candidate BSSs list is transmitted in response to the received request.

7. An IEEE 802.11 access point (AP) comprising:

a medium access controller (MAC) message generator configured to produce a MAC message having a list of candidate APs for performing a wireless transmit/receive unit (WTRU) AP selection, the candidate APs list comprising an identity of each AP and a preference indicator which indicates an extent that that the candidate AP is preferred for selection and whether the candidate AP shall not be considered for selection; and

a transceiver configured to transmit the MAC message.

8. The IEEE 802.11 AP of claim 7 wherein the candidate APs list indicates a frequency channel of each candidate AP.

9. The IEEE 802.11 AP of claim 7 wherein the candidate APs list indicates for each candidate AP a channel occupancy of that AP.

10. The IEEE 802.11 AP of claim 7 wherein the transceiver is configured to transmit an expiration time associated with the candidate BSSs list.

11. The IEEE 802.11 AP of claim 7 wherein the candidate APs list is sent in a body of a MAC frame.

12. The IEEE 802.11 AP of claim 7 wherein the transceiver is configured to receive a request for the candidate APs list and the MAC message is transmitted in response to the received request.

13. A wireless local area network (WLAN) wireless transmit/receive unit (WTRU) comprising:

a transceiver configured to received a list of candidate basic service sets (BSSs); and

a medium access controller (MAC) configured to receiver the list of candidate BSSs list for use in performing BSS selection, the candidate BSSs list including an identity of each candidate BSS and a preference indicator which indicates an extent that that candidate BSS is preferred for selection and whether the candidate BSS shall not be considered for selection.

14. The WLAN WTRU of claim 13 wherein the candidate BSSs list indicates a frequency channel of each candidate BSS.

15. The WLAN WTRU of claim 13 wherein the candidate BSSs list indicates for each candidate BSS a channel occupancy of that BSS.

16. The WLAN WTRU of claim 13 wherein the transceiver is configured to receive an expiration time associated with the candidate BSSs list.

17. The WLAN WTRU of claim 13 wherein the candidate BSSs list is received in a body of a MAC frame.

18. The WLAN WTRU of claim 13 wherein the transceiver is configured to transmit a request for the candidate BSSs list and the candidate BSSs list is received in response to the transmitted request.

19. An IEEE 802.11 station comprising:

a transceiver configured to receive a medium access control (MAC) message; and

a MAC message receiver configured to receive the MAC message that has a list of candidate access points (APs) for performing access point (AP) selection, the candidate APs list comprising an identity of each AP and a preference indicator which indicates an extent that the candidate AP is preferred for selection and whether the candidate AP shall not be considered for selection.

20. The IEEE 802.11 station of claim 19 wherein the candidate APs list indicates a frequency channel of each candidate AP.

21. The IEEE 802.11 station of claim 19 wherein the candidate APs list indicates for each candidate AP a channel occupancy of that AP.

22. The IEEE 802.11 station of claim 19 wherein the transceiver is configured to receive an expiration time associated with the candidate BSSs list.

23. The IEEE 802.11 station of claim 19 wherein the candidate APs list is received in a body of a MAC frame.

24. The IEEE 802.11 station of claim 19 wherein the transceiver is configured to transmit a request for the candidate APs list and the MAC message is received in response to the transmitted request.

25. A method for use in a wireless local area network (WLAN) comprising:

receiving a list of candidate basic service sets (BSSs) in a medium access control (MAC) message at a wireless transmit/receive unit (WTRU), the candidate BSSs list including an identity of each candidate BSS and a preference indicator which indicates an extent that the candidate BSS is preferred for selection and whether that candidate BSS shall not be considered for selection; and

selecting a BSS by the WTRU using the candidate BSSs list.

26. The method of claim 25 wherein the candidate BSSs list indicates a frequency channel of each candidate BSS.

27. The method of claim 25 wherein the candidate BSSs list indicates for each candidate BSS a channel occupancy of that BSS.

28. The method of claim 25 further comprising receiving by the WTRU an expiration time associated with the candidate BSSs list.

29. The method of claim 25 wherein the candidate BSSs list is received in a body of a MAC frame.

30. The method of claim 25 further comprising transmitting a request for the candidate BSSs list and the candidate BSSs list is received in response to the transmitted request.

31. In a wireless communication system including a plurality of access points (APs) and a wireless transmit/receive unit (WTRU) currently associated with a first one of the APs, a method of reselecting a second one of the APs to be associated with the WTRU, the method comprising:

(a) the first AP sending at least one AP reselection policy to a WTRU;

(b) if the WTRU is operating in an open state, the WTRU performing measurements in accordance with the AP reselection policy;

(c) the WTRU determining whether results of the measurements satisfy a condition defined by the AP reselection policy for reselecting the second AP; and

(d) the WTRU performing reselection of the second AP if the determination at step (c) is positive.

32. The method of claim 31 wherein the AP reselection policy requires a measurement to be taken, a margin by which a value of the measurement for the second AP must exceed a corresponding value for the first AP and a duration for which the margin has to be exceeded before reselection of the second AP is performed.

33. The method of claim 32 wherein the AP reselection policy includes at least one of a list of candidate APs to perform reselection of and a list of frequency channels on which the candidate APs operate.

34. The method of claim 32 wherein the AP reselection policy specifies whether the AP reselection policy applies when the WTRU is in an associated state, in an authenticated but unassociated state or in an unauthenticated and unassociated state.

35. The method of claim 32 wherein the measurement includes at least one of a load metric indicating an amount of radio resources that are used, a received signal power level, a signal-to-noise ratio (SNR), a signal-to-interference ratio (SIR), an expected instantaneous data rate and expected average throughput.

36. The method of claim 35 wherein the load metric is based on at least one of a channel-based load metric and an AP-based load metric.

37. The method of claim 31 wherein the WTRU uses at least two AP reselection policies in combination.

38. The method of claim 31 wherein at least two AP reselection policies are sent to the WTRU and the AP specifies whether the reselection takes place when any, or all, of the policies have its conditions satisfied.

39. The method of claim 31 wherein the AP reselection policy includes a valid time period for the AP reselection policy.

40. The method of claim 31 wherein the WTRU operates in either an open state or a closed state, the WTRU performing the measurements in accordance with the AP reselection policy only when operating in the open state.

41. The method of claim 31 wherein steps (c) and (d) are not executed if the WTRU is operating in a closed state.

42. The method of claim 40 wherein the state of the WTRU is switched between the open state and the closed state when a triggering condition is met.

43. The method of claim 42 wherein the triggering condition is monitored by either the WTRU or the first AP.

44. The method of claim 42 wherein the triggering condition is met when at least one of an error rate, a medium access delay, a data rate of received packet, a data rate of transmitted packet, a contention window size, channel occupancy, a rate of failed packet reception, a received signal strength indicator, a received signal code power, a signal-to-noise ratio (SNR) and a signal-to-interference ratio (SIR) reaches a corresponding threshold for a predetermined time period.

45. The method of claim 44 wherein the AP detects the triggering condition and sends a signal to the WTRU, whereby the state of the WTRU is switched in accordance with the signal.

46. The method of claim 45 wherein the signal is sent via a physical layer or a medium access control (MAC) layer.

47. The method of claim 31 wherein the AP reselection policy is sent to the WTRU in response to the AP receiving a request from the WTRU.

48. The method of claim 31 wherein the WTRU notifies the first AP of the reselection of the second AP.

49. A wireless communication system for reselecting a candidate access point (AP) for association with a wireless transmit/receive unit (WTRU) that is currently associated with an originally selected AP, the system comprising:

a plurality of APs, each AP comprising an AP reselection policy controller for establishing and sending at least one AP reselection policy to the WTRU; and

the WTRU comprising;

a measurement unit for performing measurements in accordance with the AP reselection policy when the WTRU is operating in an open state; and

an AP selection controller for determining whether results of the measurements satisfy a condition defined by the AP reselection policy for reselecting the candidate AP to be associated with the WTRU, whereby the WTRU performs reselection of the candidate AP if the condition defined in the AP reselection policy is satisfied.

50. The system of claim 49 wherein the AP reselection policy requires a measurement to be taken, a margin by which a value of the measurement for the candidate AP must exceed a corresponding value for the originally selected AP and a duration for which the margin has to be exceeded before reselection of the candidate AP is performed.

51. The system of claim 50 wherein the AP reselection policy further includes at least one of a list of candidate APs to perform reselection of and a list of frequency channels on which the candidate APs operate.

52. The system of claim 50 wherein the AP reselection policy specifies whether the AP reselection policy applies when the WTRU is in an associated state, in an authenticated but unassociated state or in an unauthenticated and unassociated state.

53. The system of claim 50 wherein the measurement includes at least one of a load metric indicating an amount of radio resources that are used, a received signal power level, a signal-to-noise ratio (SNR), a signal-to-interference ratio (SIR), an expected instantaneous data rate and expected average throughput.

54. The system of claim 53 wherein the load metric is based on at least one of a channel-based load metric and an AP-based load metric.

55. The system of claim 49 wherein the WTRU uses at least two AP reselection policies in combination.

56. The system of claim 49 wherein at least two AP reselection policies are sent to the WTRU and the AP specifies whether the reselection takes place when any, or all, of the policies have its conditions satisfied.

57. The system of claim 49 wherein the AP reselection policy includes a valid time period for the AP reselection policy.

58. The system of claim 49 wherein the WTRU operates in either an open state or a closed state, the WTRU performing the measurements in accordance with the AP reselection policy only when operating in the open state.

59. The system of claim 58 wherein the measurement unit and the AP selection controller are not activated when the WTRU is operating in a closed state.

60. The system of claim 58 wherein the state of the WTRU is switched between the open state and the closed state when a triggering condition is met.

61. The system of claim 60 wherein the WTRU and the AP monitor the occurrence of the triggering condition.

62. The system of claim 60 wherein the triggering condition is met when at least one of an error rate, a medium access delay, a data rate of received packet, a data rate of transmitted packet, a contention window size, channel occupancy, a rate of failed packet reception, a received signal strength indicator, a received signal code power, a signal-to-noise ratio (SNR) and a signal-to-interference ratio (SIR) reaches a corresponding threshold for a predetermined time period.

63. The system of claim 62 wherein the AP detects the triggering condition and sends a signal to the WTRU, whereby the state of the WTRU is switched in accordance with the signal.

64. The system of claim 63 wherein the signal is sent via a physical layer or a medium access control (MAC) layer.

65. The system of claim 49 wherein the AP reselection policy is sent to the WTRU in response to the AP receiving a request from the WTRU.

66. The system of claim 49 wherein the WTRU notifies the originally selected AP of the reselection of the candidate AP.

67. In a wireless communication system including a plurality of access points (APs) and a wireless transmit/receive unit (WTRU) currently associated with a first one of the APs, a method of reselecting a second one of the APs to be associated with the WTRU, the method comprising:

(a) the WTRU requesting the first AP for an AP-reselection policy, triggers and configuration parameters;

(b) the first AP sending an AP-reselection policy, triggers and configuration parameters to the WTRU;

(c) the WTRU evaluating the AP-reselection triggers;

(d) the WTRU notifying the first AP of the occurrence of a trigger condition and identification information regarding the second AP; and

(e) re-associating the WTRU with the second AP.

68. A wireless communication system comprising:

(a) a first access point (AP);

(b) a second AP; and

(b) a wireless transmit/receive unit (WTRU) currently associated with the first APs, wherein the WTRU requests the first AP for an AP-reselection policy, triggers and configuration parameters, the first AP sends an AP-reselection policy, triggers and configuration parameters to the WTRU, the WTRU evaluates the AP-reselection triggers, the WTRU notifies the first AP of the occurrence of a trigger condition and identification information regarding the second AP, and the WTRU is re-associated with the second AP.

69. A wireless transmit/receive unit (WTRU) comprising:

a transceiver configured to received a list of candidate basic service sets (BSSs);

wherein the WTRU roams to a BSS selected from the list of candidate BSSs.

70. The WTRU of claim 69 wherein the candidate BSSs list includes an identity of each candidate BSS and a preference indicator indicating an extent that that candidate BSS is preferred for selection and whether that candidate BSS shall not be considered for selection

71. The WTRU of claim 69 wherein the candidate BSSs list indicates a frequency channel of each candidate BSS.

72. The WTRU of claim 69 wherein the candidate BSSs list indicates for each candidate BSS a channel occupancy of that BSS.

73. The WTRU of claim 69 wherein the transceiver is configured to transmit an expiration time associated with the candidate BSSs list.

74. The WTRU of claim 69 wherein the candidate BSSs list is sent in a body of a MAC frame.

75. The WTRU of claim 69 wherein the transceiver is configured to receive a request for the candidate BSSs list and the candidate BSSs list is transmitted in response to the received request.